Shoulder milling cutting means milling cutting where an insert angle of a cutting insert with respect to a work-piece is 90°. U.S. Pat. No. 7,604,441 discloses a conventional double-sided cutting insert for shoulder milling cutting. FIGS. 1-3 show the cutting insert (I) as disclosed in U.S. Pat. No. 7,604,441.
As shown in FIGS. 1 and 2, the cutting insert (I) comprises two facing end surfaces (2) and four side surfaces (3), which connect the end surfaces. Both end surfaces (2) have an identical shape and a generally square shape when viewed from a vertical perspective. Also, the four side surfaces (3) have the identical shape as each other and are a diagonally-symmetrical structure with respect to a median plane (M). Each side of the end surface (2) comprises a cutting edge (4) and a wiper edge (5). That is, the cutting insert (I) has a total of eight cutting edges (4) and eight wiper edges (5). As shown in FIG. 2, each cutting edge (4) extends obliquely from a corner toward the median plane (M). Each wiper edge (5) upwardly extends from the end of the cutting edge (4) beyond the end surface (2).
The cutting insert (I) is configured to be mounted on an insert pocket of a milling cutter so as to have a negative axial relief angle and a negative radial relief angle since it is double-sided. The cutting edge (4) extends obliquely from the corner toward the medial plane (M). As such, at said mounting position, the cutting edge (4) is disposed in a positive axial rake angle with respect to a work-piece. Also, since the wiper edge (5) is higher than the end surface (2), a wiper clearance (WC), which is required in said mounting position, is secured. Thus, the cutting insert (I) can perform the 90° shoulder milling cutting.
FIG. 3 shows shoulder milling cutting of said cutting insert (I). The cutting insert (I) mounted on an insert pocket of a milling cutter has a problem since a non-operative wiper edge (5) protrudes in a radially outward direction of the milling cutter. Since the non-operative wiper edge (5) protrudes in a radially-outward direction of the milling cutter compared to the operative cutting edge (4), the cutting depth of the cutting insert (I) is limited to be a depth such that the protruding non-operative wiper edge (5) may not intervene with the work-piece.